1. Field of the Invention
The invention concerns a device and method for two-way, simultaneous digital communication between a “master” transmitter and at least one “slave” transmitter, connected by an active connection wire (a transmitter being defined as an emitter/receiver pair).
One application of the communication device and method concerns the interfacing between at least two devices via a single connector (for example, an electronic key and an electronic lock).
2. Description of the Related Art
Numerous techniques enabling several electronic systems to communicate exist. The choice of a particular technique depends on the technical constraints of the environment, for example: transmission speed, distance between the systems, electrical power available for the transmission means, communication medium (radio, infrared, wire, etc.) and their characteristics (shielded cable, optical fibre, etc.).
The U.S. Pat. Nos. 5,619,066 and 5,517,015 describe communication devices and methods on a single wire between a master system (host) and a slave system (module).
Another known communication method is “half duplex” communication. The master system transmits energy and information to a slave system. The slave system accumulates data and energy. The slave system transmits its information to the master system using the energy previously accumulated.
These solutions present disadvantages, especially regarding the serious limitations concerning the power transmitted and costs. The energy recovered from the signal sent by the master system (host) is in fact stored in a capacitor. The use of a high-value capacitor (several nanofarads) is expensive on an integrated circuit. In addition, use of a capacitor is accompanied by residual ripple, incompatible with digital technology.
Lastly, another known communication device such as the telephone can be used for two-way, simultaneous data transmission and energy transmission. Continuous polarisation of the telephone line supplies power to the user's telephone set remotely. The combination of the upline signals (from the public network to the user's telephone set) and downline signals (from the user's telephone set to the public network) forms a composite voltage signal. The downline or upline signal, respectively, can be generated by knowing the composite signal and one of the two signals, upline or downline.